Optically excitable luminescent sensor elements

Abstract

A sensor element adaptable for measurement of a physical parameter formed of a crystalline material and emitting luminescent spectra upon excitation by light spectra and the influence of said physical parameter. A first layer emitting luminescent spectra is formed of a semiconductor material containing dopant providing shallow energy levels and recombination centers with a concentration between 10 15 to 10 18 cm -3 , and sandwiched between second and third layers of semiconductor material having low absorption for light excitation of the first layer, and the respective lattice constants of the second and third layers being substantially coincidental with the lattice constant of the first layer. The sensor element is formed of GaAs for the substrate and AlGaAs for the semiconductor layers, with appropriate variation in the concentration Al, Ga, and As for the various layers. Generally, the energy band gap of the layers sandwiching the luminescent emitting layer are higher than that of the emitting layer. In a modified embodiment, GaAs is used as the luminescence emitting layer with covering semiconductor layers of AlGaAs, with appropriate variation in the concentration of Al, Ga and As. In a further modification an additional semiconductor layer of AlGaAs is sandwiched between the active semiconductor layer and a non-active semiconductor layer to reduce or eliminate a shift in the wavelength emission of the sensor element.

What is claimed is: 
     
       1. A sensor element adaptable for measurement of a physical parameter, formed of a crystalline material and emitting luminescence spectra, comprising: a first semiconductor layer composed of Al y  Ga 1-y  As for emitting luminescence spectra upon excitation by light spectra and the influence of said physical parameter, and having a dopant concentration between 10 15  to 10 18  cm -3  ;   a second semiconductor layer composed of Al z  Ga 1-z  As formed over said first layer;   a third semiconductor layer composed of Al x  Ga 1-x  As formed under said first layer;   said second and third semiconductor layers each having low absorption for the light excitation and light emission of said first layer, the respective lattice constants of the second and third semiconductor layers substantially coinciding with the lattice constant of said first semiconductor layer;   where 0<x<0.6, 0<y<0.3, and 0<z<0.6; and   said first, second and third layers being of the same conductivity type.   
     
     
       2. A sensor element as claimed in claim 1 further comprising a substrate supporting said first, second and third semiconductor layers and formed of GaAs semiconductor material. 
     
     
       3. A sensor element adaptable for measurement of a physical parameter and formed of a crystalline material, comprising: a first semiconductor layer composed of GaAs for emitting luminescence spectra upon excitation by light spectra and the influence of said physical parameter;   second and third semiconductor layers formed of Al x  Ga 1-x  As and sandwiching said first semiconductor layer, each said second and third semiconductor layer having low absorption for the light excitation and light emission of said first layer, the respective lattice constants of the second and third semiconductor layers substantially coinciding with the lattice constant of said first semiconductor layer;   where 0<x<0.6;   a semiconductor substrate formed of GaAs supporting said first, second and third semiconductor layers; and   said first, second and third semiconductor layers being of the same conductivity type.   
     
     
       4. A sensor element as claimed in claim 3 further comprising a fourth semiconductor layer composed of Al y  Ga 1-y  As sandwiched between said first and third semiconductor layers formed on top of said substrate and wherein 0<y<0.3. 
     
     
       5. A sensor element in a fiber optic sensor system, adaptable for the measurement of one of temperature and pressure and formed of a crystalline material, comprising: a first semiconductor layer composed of Al y  Ga 1-y  As for emitting luminescence spectra upon excitation by light spectra and the influence of one of said temperature and pressure, and having a dopant concentration between 10 15  to 10 18  cm -3  ;   a second semiconductor layer composed of Al z  Ga 1-z  As formed over said first layer;   a third semiconductor layer composed of Al x  Ga 1-x  As formed under said first layer;   said second and third semiconductor layers each having low absorption for the light excitation and light emission of said first layer, the respective lattice constants of the second and third semiconductor layers substantially coinciding with the lattice constants of said first semiconductor layer;   where 0<x<0.6, 0<y<0.3, and 0<z<0.6; and   said first, second and third semiconductor layers being of the same conductivity type.   
     
     
       6. A sensor element as claimed in claim 5 further comprising a substrate supporting said first, second and third semiconductor layers and formed of GaAs semiconductor material. 
     
     
       7. A sensor element in a fiber optic sensor system, adaptable for the measurement of one of temperature and pressure and formed of a crystalline material, comprising: a first semiconductor layer composed of GaAs for emitting said luminescence spectra upon excitation by light spectra and the influence of one of said temperature and pressure;   second and third semiconductor layers formed of Al x  Ga 1-x  As and sandwiching said first semiconductor layer, each said second and third semiconductor layer having low absorption for the light excitation and light emission of said first layer, the respective lattice constants of the second and third semiconductor layers substantially coinciding with the lattice constants of said first semiconductor layer;   where 0<x<0.6;   a semiconductor substrate formed of GaAs supporting said first, second and third semiconductor layers; and   said first, second and third semiconductor layers being of the same conductivity type.   
     
     
       8. A sensor element as claimed in claim 7, further comprising a fourth semiconductor layer composed of Al y  Ga 1-y  As sandwiched between said first and third semiconductor layers formed on top of said substrate and wherein 0<y<0.3. 
     
     
       9. A sensor element formed of a crystalline material and adaptable for measuring a physical parameter such as one of temperature and pressure, comprising: at least three semiconductor layers;   a first semiconductor layer emitting luminescence upon excitation by light spectra and a change in said physical parameter, and at least one first dopant material providing shallow energy levels and with at least one second dopant material providing recombination centers, the concentration of said first dopant being between 10 15  to 10 18  cm -3  ;   at least second and third layers of semiconductor material surrounding said first layer and having low absorption for the light excitation and light emission of said first layer, the respective lattice constants of said second and third semiconductor layers substantially coinciding with the lattice constant of said first layer; and   each of said at least three semiconductor layers having the same type of majority charge carriers.   
     
     
       10. A sensor element as claimed in claim 9, wherein said first layer is formed of GaAs as the semiconductor material. 
     
     
       11. A sensor element as claimed in claim 9, further comprising a fourth layer forming a substrate supporting said at least three semiconductor layers and being adjacent to one of said second and third layers. 
     
     
       12. A sensor element as claimed in claim 9, further comprising a fourth layer forming a substrate of GaAs, and supporting said at least three semiconductor layers and being adjacent one of said second and third layers, and wherein at least one of said second and third layers has a greater band gap than the band gap of said first layer. 
     
     
       13. The sensor element as claimed in claim 12, wherein said first layer is grown from a GaAs melt and having a greater thickness than said second and third layer. 
     
     
       14. The sensor element as claimed in claim 13, further comprising an additional layer formed between said first layer and at leasd one of said second and third layers, said first layer having a higher dopant concentration and a greater thickness than one of said second and third layers between which said additional layer is formed. 
     
     
       15. A sensor element as claimed in claim 9, wherein said first semiconductor layer is doped with both said first and second dopants, each being selected from the group consisting of Si, Mg and Ge. 
     
     
       16. A sensor element adaptable for measurement of a physical parameter and formed of a crystalline material, comprising: a first semiconductor layer composed of Al y  Ga 1-y  As for emitting luminescence spectra upon excitation by light spectra and the influence of said physical parameter, and having a dopant concentration between 10 15  to 10 18  cm -3  ;   a second semiconductor layer composed of Al z  Ga 1-z  As formed over said first layer;   a third semiconductor layer composed of Al x  Ga 1-x  As formed under said first layer;   where 0<x<0.6, 0<y<0.3 and 0<z<0.6; and   said first, second and third layers being of the same conductivity type.   
     
     
       17. A sensor element as claimed in claim 16, wherein said physical parameter is one of temperature and pressure. 
     
     
       18. A sensor element as claimed in claim 16, further comprising a substrate supporting said first, second and third semiconductor layers and formed of GaAs semiconductor material. 
     
     
       19. A sensor element as claimed in claim 18, wherein said physical parameter is one of temperature and pressure. 
     
     
       20. A sensor element adaptable for measurement of a physical parameter and formed of a crystalline material, comprising: a first semiconductor layer composed of GaAs for emitting luminescence spectra upon excitation by light spectra and the influence of said physical parameter;   second and third semiconductor layers formed of Al x  Ga 1-x  As and sandwiching said first semiconductor layer;   where 0<x<0.6;   a semiconductor substrate formed of GaAs supporting said first, second and third semiconductor layers; and   said first, second and third semiconductor layers being of the same conductivity type.   
     
     
       21. A sensor element as claimed in claim 20, wherein said physical parameter is one of temperature and pressure. 
     
     
       22. A sensor element as claimed in claim 20, further comprising a fourth semiconductor layer composed of Al y  Ga 1-y  As sandwiched between said first and third semiconductor layers formed on top of said substrate, and wherein 0<y<0.3. 
     
     
       23. A sensor element as claimed in claim 22, wherein said physical parameter is one of temperature and pressure.